Endometriosis is an estrogen dependent disease. Current medical therapies to inhibit estrogen biosynthesis and actions fail to prevent reoccurrence of the disease and compromise success of pregnancy in child-bearing age women. This suggests a crucial need to identify potential cell signaling pathways for nonestrogen therapeutic targets for endometriosis. Prostaglandin E2 (PGE2) promotes survival of endometriosis, however; the underlined molecular mechanisms are largely unknown. Our long-term goal is to understand molecular and cellular aspects of PGE2 biosynthesis and signaling cross-talk in the pathogenesis of endometriosis in order to identify new targeted therapies. The objective of this application is to understand PGE2 signaling pathways in survival and growth of endometriosis. Our central hypothesis is that loss-of-function of PGE2 receptors EP2 and EP4 inhibits survival and growth of endometriosis. Specific Aim-1 will determine the mechanisms through which loss-of-function of EP2 and EP4 induces apoptosis of endometriosis. Specific Aim- 2 will determine the mechanisms through which EP2 and EP4-mediated PGE2 signaling immunomodulate and enhance the phagocytic ability of macrophages in endometriosis. Specific Aim-3 will determine the mechanisms through which loss-of-function of EP2 and EP4 decrease estrogen production in endometriosis. Our experimental approaches include: (i) genomic and pharmacological inhibition of EP2 and EP4; (ii) stable fluorescence-labeled human endometriotic epithelial cells, stromal cells, macrophages, and eutopic and ectopic endometria from endometriosis patients, (iii) nude and Rag2g(c) mice xenograft models, (v) molecular, cellular, biochemical, and microscopy-based assays; and (vi) whole animal bioimaging method. The rationale is that successful completion of the proposed research will contribute a missing and fundamental element to our base of knowledge without which the mechanism through which selective inhibition of EP2 and EP4 induces apoptosis of human endometriotic cells cannot be understood. In addition, the expected results will advance the current knowledge of the pathogenesis of endometriosis and increase the understanding of PGE2 signaling in survival of endometriosis. The acquisition of such knowledge is critical and could be translated to treat women suffering from endometriosis. It is our expectation that selective inhibition of EP2 and EP4 will induce apoptosis of endometriotic cells, increase phagocytic ability of infiltrated macrophages in endometriosis per se, and decrease estrogen production by the endometriotic cells through multiple mechanisms. Our findings would have clinical impact because it would allow for the first time to develop new and much needed therapeutic strategies to inhibit EP2 and EP4 signaling as novel nonestrogen targets for the treatment of endometriosis in child-bearing age women. This is a R21 application addresses the mission of NIH/NICHD on women's reproductive health.